Answers

2016-02-14T08:38:03+05:30
Speed=340m/s
distance=20m
threfore, time=dist/speed
                     =340/20
                     =17s

the frequency=280hz
therefore, no. of vibrations in 1s=280

Therefore, total no. of vibrations in 20m=280 x 17
                                                               =4760 vibrations.
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